This invention relates to an inference based automatic transmission shift pattern control.
Shifting in a multi-speed ratio automatic transmission is typically initiated in response to the detection of predefined vehicle speed and engine load conditions, referred to collectively as a shift pattern. Typically, upshift and downshift vehicle speed thresholds are determined as a function of an engine load parameter such as throttle position. An upshift is initiated if the actual vehicle speed exceeds the upshift threshold, and a downshift is initiated if the actual vehicle speed is lower than the downshift threshold.
During cruise control operation wherein the vehicle is controlled to a set speed, resumes a previously selected set speed or is accelerated to a higher set speed, reliance upon typical shift pattern control may undesirable result in overshoot of set speed, downshifts for relatively small and consistent speed deviation from set speed, and frequent shifting when the road load exceeds the torque delivery capacity of the drivetrain.
Shift controls are known which adhere to conventional shift pattern methodology in cruise control, differing however with the substitution of alternate vehicle speed versus engine load calibrations. While offering some improvement, substitution of alternate calibrations ultimately suffers from similar shortcomings, only at different vehicle speed versus engine load conditions.